Dr. Eilish Cleary says two cases have been reported in the Saint John area and three more were in the Fredericton area.
The infected people all showed up at local emergency rooms, but only one has been admitted to hospital.
Symptoms of the gastro-intestinal illness include severe cramps, bloody diarrhea and vomiting.
To prevent the infections from spreading, Cleary says people should wash their hands thoroughly after using the washroom or changing diapers.
Other precautions include washing and peeling raw vegetables and fruits, thoroughly cooking all meats and to prevent contact between cooked foods and raw poultry and other meats.
Last July, public health officials said they were unable to determine the source of an E. coli outbreak that affected four people in New Brunswick.
In those cases and the more recent ones the strains of E. coli were the same as the one found during the Walkerton, Ont., water disaster in 2000 that killed seven people.